Strand twisting machine



l. S. ROBERTS STRAND TWISTING MACHINE July 10, 1951 4 Sheets-Sheet 1 Filed Dec. 16, 1947 4k INVENTOR.

/NGHAM 5. ROBERTS July 10, 1951 l. s. RoBERTs STRAND TWISIING MACHINE 4 Sheets-Sheet 2 Filed Dee. 16, 1947 n l firk J7 .fa-

. INVENTOIL /NGHAM `S. ROBE /iT` l. S. ROBERTS STRAND TWISIING MACHINE July 1o, 1951 4 Sheets-Sheet 3 Filed Dec. 16. 1947 INVENTOR. -/NeHAM s; Rosen Ta BY Patented July 10, 1951 STRAND TWISTING MACHINE Ingham Roberts, Ridley Park, Pa., assignor to American Viscose Corporation, Wilmington, Del., a corporation of Delaware Application December 16, 1947, Serial No. 791,963

7 Claims.y (Cl. 57-58) This invention relates to yarn or thread twistlng machinery such as a two-for-one twister and particularly to devices for controlling yarn or thread tension during a twisting operation.

In a typical two-for-one twisting operation, a, strand such as a thread, cord, ply or yarn is pulled from a supply package through the twister and is wound about the spindle of a package winding machine. More explicitly, untwisted or partially twisted yarn is supplied from a supply package, such as a bobbin, cake, or cheese held in place on the twister by a holder mounted on the twister spindle but held from rotating during the twisting operation. Yarn is drawn from the non-rotating supply package into one end of the rapidly rotating hollow twister spindle, then withdrawn at another point by a flyer and delivered to a rotating eccentric position. AS the spindle is rotated, the yarn which progressively passes between the flyer and an overhead ring guide is acted upon by forces which cause it to follow a spiral path. This spiral path revolves about the axis to form an apparent balloon outline which is usually referred to as a balloonJ From the overhead ring guide, the yarn passes to the package winding machine.

In adapting twisting machines of this type to the processing of large packages, large stable balloons must be formed to provide space for package holders of suflicient size. Other factors being constant, the shape of the balloon and the volume enclosed by it are determined by the tension in the strand; a high strand tension produces a narrow balloon with a relatively large mean helix angle while a low strand tension produces a wide balloon with a relatively small mean helix angle. Thus, to secure a balloon which will encompass a large supply package, as well as to avoid overstraining the yarn, it is desirable that the twisting be conducted at low strand tension. However, low strand tensions are more difficult to maintain than high strand tensions since variations in absolute tension values have relatively larger percentage effects. Also, the small helix angle balloon resulting from low strand tension is relatively unstable since the strand length in the balloon is greater. It is therefore readily apparent that provision must be made for precise tension control if large supply packages are to be twisted on a machine of this type. The present invention provides means for securing this precise tension control.

The problem of balloon shape control and the operation of the present invention can be more fully understood through consideration of the forces which act on the strand as it revolves about the spindle axis in passing between the yer and the ring guide and which, vin combination, cause it to assume a certain denite shape. There are four such forces to be considered, i. e., the draft which is imposed on the strand by the take-up means, centrifugal force, wind resistance to peripheral motion, and the retarding force which is applied to the strand at or before the flyer by frictional resistance or other means. A fifth force, wind resistance to motion lengthwise of the strand, is negligible and the draft may therefore be considered to be equal to the retarding force and both of them to be equal to the tension in the strand. The centrifugal force on the strand is a function of spindle speed, mean balloon diameter, balloon height, strand denier and strand moisture content and the wind resistance to peripheral motion is a function of spindle speed, air humidity, mean balloon diameter, balloon height, degree of twist being applied and strand denier, lament count, filament structure, material density, finish and original twist. However, all of these factors except balloon diameter may be readily maintained substantially constant and the balloon diameter becomes xed when the strand tension is made fixed. If, for a given system of the general character described, the above mentioned factors, with the exception of strand tension and balloon diameter, are maintained constant and the strand tension is decreased a definite small amount by reducing the retarding force, the balloon diameter will increase and its mean helix angle will decrease until a new balance of forces is obtained and a new stable balloon shape is secured. This decrease in balloon helix angle with decrease in strand tension has an important bearing upon the invention as explained later.

An important object is to provide a two-stage tensioning device for a two-for-one twister which produces greater uniformity in yarn tension and improved balloon characteristics. As objects ancillary thereto, a simple and inexpensive device is provided for initially tensioning the yarn before or as it enters the hollow twister spindle; to accomplish second stage tensioning, a yer of particular design for producing desired frictional effects is also provided. It is an object also to accomplish tensioning of yarn or thread during the twisting with a minimum of disturbance to the yarn structure or iilaxnent arrangement. It is also an object to provide an electrical means for effecting emergency stopping of twisting machinery. Another object is to provide the above means while maintaining standard design features and estaras capacity for large packages. Another object is to utilize electromagnetic means which both prevents rotation of the package holder or, when failing in that function, actuates the electrical means for effecting emergency stops. @ther objects, features, and advantages will be apparent from the drawings and the following description thereof.

In the drawings illustrative of the invention,

Figure l is a side elevation partly in section of a two-for-one twisting machine embodying the invention;

Figure 2 is a perspective view of a magnetically sensitive cleat used in the machine of Figure'l;

Figure 3 is a fragmentary vertical view partly in section at right angles with the view of Figure l of the upper end of the driving shaft;

Figure 4 is a fragmentary bottom view of the flyer of Figure l showing a yarn guide in place;

Figure 5 is a fragmentary vertical section of a modied package holder and the flyer with a modified yarn guide insert in place;

Figure 6 is a perspective view of the yarn guide insert of Figures 5 and 7;

Figure 7 is a bottom view of the flyer and yarn guide insert shown in Figure 5;

Figure 3 shows a portion of a modified flyer in section;

Figure 9 is a transverse sectional view of the members of a modieol form ci initial tension= ing device;

Figure l illustrates a variation of the device shown in Figure 9; A

Figure lil is a top view of an initial tensioning device;

Figure l2 is a side elevation in section of another embodiment of the invention;

Figure i3 is an electrical circuit diagram of the invention;

Figure la is a partial elevation of a twisting machine and illustrates a helical yarn path.

Figure l is a proile in a vertical plane of the strand-guiding portion oi a yer; and

Figure i6 shows the area ci the strand-guiding flyer portion of Figure l5 developed in a plane.

Referring now to Figure l, a two-for-one twisting machine is shown comprising as its principal parts, a driving means such as an elec tric motor I2, a drive shaft i3, a hollow tubular, shaft I4, a package holder i5, and a flyer i6. A ring-guide I9 is supported rigidly above the ma chinel by means not shown. Since the various parts of the machine are ysupported either by the driving means housing I'! or the shaft i3, the

machine may receive its principal support at the driving means housing I'I by supporting means such as the platform or rail I la. The upper end of the drive shaft I3 terminates in a groove oblique to its axis. The hollow spindle shaft I4 has an enlarged portion 22 which fits tightly over the upper end of shaft I3. The shaft I3 is drilled axially from the portion of the grooved surface nearest the driving means to accommodate the two ends of a U-shaped member 2I as shown in Figures 1 and 3. Spindle shaft I4 has an enlarged lower portion 22 which provides close-fitting and limited telescopic relation with the shaft I3 on the interior and forms an exterior shoulder 23 whereby the axial position of the flyer I5 is determined. Shaft I4 is at least long enough to provide stable support of the package holder I5 at the bearings 26 and 21. The enlarged portion 22 of shaft I4 is provided with an opening 22a aligned with the closed end of U-shaped member 2I so that yarn or thread may be introduced into the top end of shaft I4 and discharged beneath the flyer I6.

The holder I5 comprises a base portion 30 acting as a hub about the bearing 21, a lower cylindrical shell member 3l having a flange extending inwardly from its lower portion and secured thereby to the top surface, of base portion 3D. an upper hub member 35 for bearing 26, and a cylindrical sleeve 33 connecting the base portion 30 and the hub member 35. The shell member 3l is provided with a chrome plated and polished outer flange 32 about its top portion for minimizing frictional contact and abrasion of the strand with the supply holder assembly during starting and stopping of the twisting machine. To prevent the material being twisted from coming into contact with a supply package 41 or with the yarn being drawn therefrom, a domed or conical cover such as the shell member 34 is supported on a horizontal surface 4@ formed by an annular recess along the inner surface in the top portion of member 3l. So that strands on the bottom portion of the supply package do not become damaged and so that the supply package is prevented from easily rotating about the smooth metal surface of the bottom of the shell member 3|, an annular hat cushion 43 of felt or other soft protective material is placed within the member 3l at the package supporting surface. A supply package of yarn, or other ilarnentary or textile material is ordinarily furnished on a rigid core of standm ard design such as the cylindrical member 35 of Figure l. As both ends of the core generally extend beyond the yarn package, an annular recess 39 may be provided in the base portion 30 below the annular package-supporting surface of the member 3l to receive the lower end of the core 33. To the upper protruding end of core 35 is tted a conical or domed cap 38 having an axial passageway 3l. In order to control or restrict the path or" yarn passing into the shaft I4 and to facilitate lacing-up the passageway of cap 38 may be extended by a cylindrical member 39. i

An essential feature of the invention now to be described is the tensioning device, comprising plates 4I and 42 mounted atop the cap 38, which prevents tangling of the yarn as it passes through the rotating spindle I4 and imparts to the yarn part of the total tension necessary t0 form a stable balloon-shape such as that indicated by numeral it in Figure l. The shape of cap 38 is critically important; if it is too tall, the yarn will wrap around it and snub; if it is too short, the yarn tends to snub at the edges of the supply package. The slope of the side of the cap is then chosen so that the yarn spirals about the cap and slides smoothly and upwardly into the bite of tension plates 4I and 42. A cap having a slope of approximately 45 degrees has been found quite satisfactory although to meet specie conditions, slopes from 30 to 60 degrees with the horizontal are quite practical. Plate 42 has an annular upper yarn engaging surface and a central bore or passageway; it is firmly fastened to the cap 38 over the cap passageway 31. If desired, the plate 42 and the cap 38 may be formed as a one piece structure. Plate 4I has a lower yarn engaging surface substantially meeting the yarn engaging surface of plate 42 and has a stem 44, preferablyl tapered, extending therefrom, of smaller diameter than the passageway of plate 42. A stem diameter approximately n.80 that of the passageway diameter is quite satisfactory although stem diameters in the range of 0.10 to 0.95 that of the passageway diameter may also be used. In operation, yarn is drawn from a supply package 41 and through the tensioning device horizontally between the plates 4l and 42. While the yarn is between the mating surfaces of the plates, its longitudinal speed is from five to ten times greater than its sidewise speed depending upon the diameter of the supply package. One result thereof is a helical yarn path between plates as shown in Figure 11 which revolves once about the plate 42 for each wrap removed from the supply package. Another result is to slowly rotate the plate 4l in the direction indicated ln Figure 11 and to move it laterally so that the stem 44 rides around the wall of the passageway of the plate 42 always at a point opposite the yarn path to provide a crescent-shaped clearance space at a preferred point for yarn travel to the spindle shaft I4. This manner of operation prevents the yarn from being pinched between Lhe stem 44 and the plate 42 and from being subjected to tension variations due to spindle vibration.

The weight of the plate 4l is chosen to produce a desired tension in the yarn. Weight variation may be obtained by means of inserts of a type such as insert 48 shown in Figures 1 and 12, or small plate like discs 49 shown in Figure 9, or separale differently weighted plate units such as unit 4lb of Figure 10; a further feature embodied in the unit 41a of Figure 9 is the anti-friction element 52 which may rotate freely about a bolt 54 to reduce friction and wear on the stem and to produce, a tensioning device less sensitive to spindle vibration. 'I'he bolt 54 holds the lentire assembly together. Plate 4I and variations thereof and including attachments thereto as shown in Figures 9 and 10 are designed so that the top of the assembly does not offer obstruction to any loops of yarn which might occasionally jump over it when irregularities occur in operation. l

The tension plates 4l and 42 may be oi' an abrasion resistant material such as a vitreous ceramic material including that known by 'the trade-name Alsimag, a sintered powdered tungsten carbide including that known by the tradename Carboloy, chrome-plated steel or tungsten alloy. 'I'he mating surfaces should be ground and should have rounded corners t0 provide a smooth path for the yarn to and from the tension ntrol region. The mating surfaces should also be substantially horizontal and plane. Preferable proportions are approximately as shown; if the outside diameter of the plates is too large, the yarn wraps around the entrance groove formed at the peripheries of the mating surfaces; if the outside diameter is too small, mating surfaces are too narrow and unit pressure on the yarn becomes too great for preferred operation. Line contact between plates 4I and 42 should be used only to control very light tensions. Figure 12 illustrates the use of the invention wherein the supply package holder 15a is designed for supporting a yarn package having rusto-conical outer and inner surfaces. The upper diameter of a package insert 36a is such that the initial tensioning device plates 4l and 42 are supported directly on the insert 36a. A tubular yarn guide 39a is attached directly to plate 42. Similar members in Figures 1 and 12 are indicated by the same reference numerals; parts having similar function in the two gures but modified structure are indicated by the same reference nu- Ameral except that the letter a is added to Ithe numeral of Figure 12.

Another important feature of this invention is a flyer, such as one shown in Figures 1, 4, 5, '1, 8, and 12, designed particularly for the second stage of tensioning ln cooperation with the first stage device described hereinbefore. 'I'he flyer I6 comprises a hub portion secured to the shaft I4, a disc portion 56 which is preferably of an electrically non-conducting material, and a frustoconical rim section 51 having a flange 58, 58a, or 58h, contiguous with its smaller diameter end and an approximately cylindrical flange 59 contiguous with its larger diameter end.

As shown in Figures 1, 5, and 12, the cylindrical portion 59 is preferably 0f greater inside diameter than element 3l of the package holder so that during starting and stopping of the flyer, the yarn remains clear of the surface of the package holder assembly, or otherwise the yarn may be broken, abraded or tangledabout the twister. The rim section of ycr I6 is slotled, as shown in Figures 1, 4, and 12, for receiving a strandguiding insert 96 of abrasion resistant material, at the region where the strand passes through a right-angle or nearly right-angle turn onto the thread-guiding portion of the flyer rim. A modiiled flyer 16a with flange 58a is slotted and drilled as shown in Figures 5 and 7 to accommodate a yarn-guiding insert 62 shown removed in Figure 6. The insert 62, shown in place in Figures 5 and 7, completes a thread-guiding slot E3. The insert 96 or 62 is formed from an abrasion-resisting material such as a sintered powdered tungsten carbide including that known by the trade-name Carboloy, a tungsten steel, or a chrome-plated steel. In operation, the yarn is led from the spindle I4 around a right angle turn formed by the U-shaped insert 2|, along the underneath of disc portion 56, and through the strand-guiding insert 96 of flyer i6 onto the outer frusto-conical surface of the rim section.

The operation of the flyer to control yarn tension can best be understood from consideration of the behavior and path of the yarn upon the outer surface of the ilyer.A Figure 15 shows the outline of a center-line section of the frustoconical portion 51 and flange 58 of the ilyer. Angle Y is the generating angle of the conical surface. In Figure 16, outline EKFGLH is a development of the outside surface of portion 51. The arrow indicates the direction of rotation and point K represents the notch 63 where the yarn first contacts the face 51. Line EKF represents the flange 58 and may be considered as a partition extending upward from vthe plane of the paper for limiting the path of the yarn. The yarn, as it leaves the notch, takes a direction which is determined by the combined effect of all the forces acting upon it While in the balloon. The path of the yarn in the balloon is helical and, due to the fact that the length of yarn exposed to wind resistance progressively decreases as the yarn approaches the guide ring, the helix angle of the balloon progressively increases as shown in Figure 14. For a particular combination of operational values such as spindle speed, yarn character and yarn tension, there is a definite balance of forceson the yarn, a definite balloon shape and a denite angle of departure or initial helix angle between the path of the yarn as it leaves the ilyer surface and a tangent to the periphery of the flyer at this point. This is angle Xl in Figure 16. Since the shape of the balloon can be varied -by changing the yarn tension, as explained before, the value of angle X1 and the position of the point of departure L1 can be varied in the same manner. As the yarn tension decreases, wind resistance decreases angle X and carries point L1 to the left in Figure 16 until a point L is reached. If the point of departure is carried beyond L, as to L2, the yarn wraps around flange 58 along line FKE from K to K1 and angle X remains unchanged. This wrapping continues until the frictional resistance between the yarn and the surface of the flyer increases the yarn tension to a point where there is no further tendency for angle X to decrease in value and therefore no further tendency toward wrapping. Thus the tension in the yarn automatically assumes a balancewith the other forces on the yarn to secure a definite and constant value of angle X and a definite and constant balloon shape. Also, if the factors such as spindle speed and yarn-character which control these other forces remain constant, as they normally will during a given twisting operation, the yarn tension in the balloon will automatically remain constant if the initial tension in the yarn as it reaches the flyer does not exceed the control value.

A study of Figures and 16 will show that a definite relationship exists between angle X and the generating angle Y of the frusto-conical control surface of the flyer. This relationship Ycan be expressed by the formula where R is the radius of the flyer at the notch and W is the Width of the face of the flyer surface. Z is the angle in Fig. 16 between the radii extending from the ends of the conical surface EKFGLH of the flyer, and S represents the slope height from the smaller diameter of the conical surface of the flyer to the vertex cf the cone DOC of Fig. 15 containing the conical surface 51. The derivation of the formula is as follows:

cos X= 21rR=21rS-3%)=the circumference of the smaller This formula neglects the curvature of yarn path KL due to wind resistance and also neglects the effect of the deflection of the yarn by the rim of the flyer when point M is below the plane of the paper but it is sufficiently accurate for use to select values of R, W and Y to provide an X angle value which corresponds' to an experimentally determined acceptable balloon shape and accepttions of the flyer would become inoperative. At the other extreme, the Y value should never be high enough so that the balancing balloon tension will overstrain the yarn. In between these extremes, there is sufficient latitude so that a certain iiyer shape operating at a certain speed may be used with a reasonable variety of yarns. However, for an extreme change in yarn, such as from 150 denier to 1100 denier, Y or W, or the spindle speed must be changed (in this case, Y or W is increased or the spindle speed is decreased), if a controlled X angle and a controlled and acceptable yarn tension is to be obtained. Y values will, in practically all cases, fall within the range of 25 to 65 degrees.

The line AD in Figure 15 of surface portion 51 should preferably be straight as shown but may be made slightly concave or convex without losing its ability to control angle X. In the practice of this invention, a flyer having a yarn controlling surface sloping approximately 35 degrees with the axis and rotated at 6600 R. P. M. produced a stable balloon form with 150 denier yarn drawn at meters per minute. The yarn tension above the ring guide was approximately 22 grams. The plate weight in the initial tensioning device (plate 4i) was 10 grams. Yarn tension measured at a point between the ring guide and the take-up showed a variation under 0.5 gram.

A further important feature of this invention is the means provided for preventing turning of the package supply holder while the spindle rotates. This means comprises (1) magnetic means or magnetically sensitive elements such as steel cleats il shown fastened in an annular recess provided in the bottom surface of the base portion 30 of the package supply holder, and (2) an equal number of electromagnets 6l with pole pieces i! arranged in a similar pattern about the spindle axis closely spaced to the lower side flyer disc portion 58 and mounted on the rrotor housing l2 or other rigidly supported member related to the twisting machine. The relation of the magnetic cleats 61 to electromagnets 68 is such that as the holder I5 is rotated through one revolution, the cleats 61 are aligned with the pole pieces $9 of corresponding electromagnets in at least one position. So that the magnetic forces between adjacent pole pieces and cleats are not adversely affected when the coils of the electromagnets are energized, and to prevent the induction of eddy currents, the disc portion 56 of the flyer and the base portion 30 of the package holder are formed from non-electrically conductive materials, such as thermosetting or thermoplastic resinous compositions, resin impregnated paper or fabrics, or the electromagnets i8 may be of the single coil or the double-coil type. The double-coil type having a U-shaped core is most eifective since both of its poles terminate in a region immediately beneath the flyer. The shape of cleats i1 is most appropriate for electromagnets having a U-shaped core.

When the electromagnets Gl are energized and in alignment with elements 61, magnetic aligning forces are produced therebetween which overcome the torque produced from frictional forces generated in bearings 2i and 21 during spindle rotation. An effective holding means for av twister package holder is thus provided.

The holding means just described serves another important function of the invention, namely, as a means for actuating an electrical control system for emergency stopping of thel twisting and the packaging machinery. In ordinary operation the package holder is held from turning; however, it may be forced out of its normal alignment with the electromagnets by application of suirlcient torque; for example, bearing seizure in .bearings 2i and 21 would rotate the holder. In the event adhering, tangled, or knotted yarn on the supply package resists unwrapping therefrom, a tension is immediately produced in the yarn extending from the package to the twisting spindle which tends to or succeeds in rotating the holder out of alignment with the electromagnets. When misalignment occurs, a change of impedance is produced in the electrical circuit which energizes the coils of the electromagnets, and causes an increase in current ilow which may be used to instantaneously energize other electrical apparatus.

Referring to Figure 13, a circuit diagram is shown in which power is supplied to a twisting machine and a packagewinding device electrically controlled according to this invention from a 110 volt, 60 cycle alternating current supply comprising lines 1|) and 1 I, and a 60 volt, 3 phase alternating current supply comprising lines 12, 13, 14 through a common ve terminal plug or switch 15. The area circumscribed by a dotted line 16 indicates a 3-pole over-current relay with a thirty-two volt cnil 18. The relay contains a three-pole switch 11, the separate poles of which are indicated as Pi, P2, and P3. In a position hereinafter designated as on-power, P1, and Pz close a 3-phase power circuit to a twister motor 85 and P3 closes a two phase power circuit to a take-up means motor 84. In a position hereinafter designated as OIT-power, P1 has become functionless, P2 closes a circuit energizing a solenoid braking coil 8| and P3 closes a circuit which lights a signal 92. Holding coil 80 is used to designate the sum of the coils in the electromagnets 68. The solenoid coil 8| operates a plunger III of a braking assembly in opposition to spring to increase the impedance of the circuit containing coil 18; the relay switch 11 is thereby re- |02 (Figure l) and presses the brake shoe |03 against a brake drum |04 on shaft I3.

The circuit diagram in Figure 13 is shown for normal operation. with both motors 85 and 84 running. Assuming the plug 15, and switches 88 and 9U open, the starting procedure for the twisting machine is as follows: insert plug 15 and close switch 88. If the magnetic elements 61 of the holder I6 are not aligned with the pole pieces B9, the impedance of holding coil 88 is low enough that the current in the relay coil 18 trips the relay switch 11 to the ofi-power position and places the solenoid brake coil 8| in parallel with coil 88 so that, even if the pole pieces and electromagnets are now aligned, the'impedance of that part of the circuit would still be low enough to maintain the relay in the off-power position. If the holder and electromagnets were aligned when the switch 88 is closed, the impedance of coil 80 would be high, the switch 1I would assume on-power position, and the twister motor 85 would start. To stop the twister motor 85, switch 89 is momentarily closed to place coil 8| in parallel with holding coil 80; with the impedance of the circuit containing coil 18 reduced, the relay switch 11 trips.

To start the twister and the package Winder simultaneously, switches 90 and 88 are closed with the relay 15 in tripped position, the supply package holder is rotated for alignment of cleats 61 with the electromagnets, yarn is laced through the twister and the package winding machine, and switch 9| is momentarily opened to cut the solenoid coil 8| out of parallel with coil 80 so as turned to its normal position wherein two of its poles, P1 and Pz, close the power circuit to the three-phase twister motor and the other pole P3 closes the circuit to the winding motor 84. If it should be desired to run the winding motor 84 without the twister motor 85, close switch 90 and leave switch 88 open.

For normal stopping, push switch 89; coil 8| is thus energized and actuates the solenoid brake while also reducing the impedance; the relay trips, interrupting the power circuits to the motors 84 and 85 and closing the circuits to coil 8| and the light 92. In the case of emergency, i. e.. stopping due to bearing seizure, yarn tangling, or other cause, the supply package holder starts to rotate, and is pulled out of alignment with vthe electromagnets; impedances of the electromagnet coils decrease and the relay is tripped.

Figure 12 shows the location of permanent magnets 93 and 94 which can be used instead of cleats 81 and electromagnets 68 as an alternative means for maintaining the alignment of package holder support I5 and motor I1.

The invention described provides, in addition to the emergency stopping features, a tensioning control system which promotes unusual stability in yarn tension during a twisting operation. Variation in yarn tension may be readily limited to 0.5 gram and even less in a machine in good mechanical condition. Such control over yarn is particularly beneficial when twisting yarn furnished in large size packages since small fluctuations in yarn tension when forming large balloons at low yarn tension tend to cause relatively large changes in balloon shape. While the process for twisting ne denier, low tensile strength yarns is more beneted by the tensioning features of the invention, the twisting of all types of yarns.

threads, strands and cords is improved because of the stability imparted to the balloon and the resultant benefits of increased supply package space, and uniformity in the twisted product.

While preferred embodiments of the invention have been shown, it is to be understood that changes and variationsv may be made without departing from the spirit and scope of the invention as defined by the appended claims.

I claim:

l. A two-for-one twisting machine comprising a spindle, electrical means for driving the spindle, a yer xedv on the spindle, a supply package holder mounted on the spindle and rotatable relative thereto and provided with magnetic means, stationary electromagnetic coil means spaced with respect to the holder on the opposite side of the flyer for cooperating inductively with said magnetic means for maintaining the holder stationary, a tensioning device supported by the supply package holder, an electrically operated braking means for the spindle, electrical means electrically connected with the coil means and responsive to variations in the impedance of the coil means resulting from changes in the spacing between the magnetic means and the coil means for simultaneously operating the braking means and stopping the flow of electrical current to the driving means upon a predetermined change of said impedance, and an alternating current source for energizing the electromagnetic coil means and the electrical means.

2; A twisting machine comprising a driving shaft having a grooved oblique surface at one end, a guiding member having a strand-guiding portion spaced above the groove and extending transversely of the direction of slope of the oblique surface, a hollow extension for the drivingr shaft interiorly recessed to permit telescopic relationship therewith having an opening in radial alignment with the portion of the oblique surface below the strand-guiding portion.

3. A two-for-one twisting machine comprising a spindle, electrical means for driving the spindle, a flyer fixed on the spindle, a supply package holder mounted on the spindle and rotatable relative thereto and provided with magnetic means, stationary electromagnetic coil means spaced with respect to the holder on the opposite side of the flyer for cooperating inductively with said magnetic means for maintaining the holder stationary, electrical means electrically connected with the coil means and responsive to-variations in the impedance of the coil means resulting from changes in the spacing `between the magneticv means and the coil means'for simultaneously op.

erating the braking means and stopping the flow of electrical current to the driving means upon a predetermined change of said impedance, .and an alternating current source for energizing the electromagnetic coil means and the electrical means.

4. A two-for-one twisting machine comprising a driving shaft having an oblique surface at one end, electrical means for driving the shaft, a .guiding member having a-strand-guiding portion Aspaced above the oblique surface and extending transversely of the direction of slope of the oblique surface, a hollow extension for the driving shaft interiorly recessed to permit telescopic relationship therewith having an opening in radial alignment with the portion of the obliquo surface below the strand-guiding portion of the guiding member, a iiyer fixed to the hollow extension, a supply package holder mounted on the hollow extension and rotatable relative thereto, and provided with magnetic 'means stationary electromagnetic coil means spaced with respect to the holder on the opposite side of the flyer for cooperating inductively with said magnetic means for maintaining the holder stationary, an electrically operated braking means for the flyer, and electrical means electrically connected with the coil means, and responsive to variations in the impedance resulting from changes in the spacing between the magnetic means and the coil means for simultaneously operating the braking means and stopping the ow of electrical current to the driving means upon a predetermined change of said impedance, and an alternatingl current sourcev for energizing the electromagnetic 'coil means and the electrical means.

5. A twisting machine comprising a driving shaft having an oblique surface at one end, a driving means toward the other end thereof, a U-shaped threadguiding element attached to the end of the driving shaft within a portion of the oblique surface nearest the driving means with the thread-guiding surface of the member aligned transversely of the direction of slope of.

the oblique surface, a hollow shaft telescopically and non-rotatably attached by an enlarged end portion to the driving shaft with the interior wall of the section of smaller diameter overhanging the closed end of the U-shaped thread-guiding element, and the hollow shaft having an opening in radial alignment with the closed portion of the U-shaped member.

G. A two-for-one twisting machine comprising a spindle, electrical means for driving the spindle, a fiyer fixed on the spindle, a supply package holder mounted on the spindle and rotatable thereto and provided with magnetic means, stationary electromagnetic coil means spaced with respect to the holder on the opposite side of the flyer for cooperating inductively with said magnetic means for maintaining the holder stationary, solenoid operated braking means for the spindle, an electromagnetic coil electrically connected with the coil means, and responsive to changes in impedance of the stationary electromagnetic coil means resulting from changes in the spacing between the magnetic means and the coil means for mechanically operating the multipole switch whereby the solenoid braking means is operated and the flow of electrical current to the driving means is stopped upon a predetermined change of said impedance, and an alternating current source for energizing the electromagnetic coil means and the electrical means.

7. A two-for-one twisting machine in working relationship with an electrically driven take-up device comprising a spindle, electrical means for driving the spindle, a flyer fixed on the spindle, a supply package holder mounted on the spindle and rotatable relative thereto and provided withv magnetic means, stationary electromagnetic coil means spaced with respect to theholder on the opposite side of the ilyer for cooperating inductively with said magnetic means for maintaining the holder stationary, a solenoid operated braking means for the ilyer, an electromagnetic coil electrically connected with the coil `means and responsive to changes in impedance of the stationary electromagnetic coil means resulting from changes in the spacing between the magnetic means and the coil means for mechanically operating a multi-pole switch whereby the solenoid braking means is operated and the flow of electrical current to the driving means and the take-up means is stopped upon a predetermined change of said impedance, and an alternating current source for energizing the electromagnetic coil means and the electrical means.

INGHAM S. ROBERTS.

REFERENCES CITED The following references are of record in the le of this patent:

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